The invention is concerned generally with whirl chutes (i.e. fluidized-bed channels) for treating solid particles and more particularly it is concerned with flow leading floor for such chutes on which the treated particles are advanced under the influence of a vertical vortex of a gas in longitudinal direction from an inlet to the outlet of the chute.
For treatment of solid particles such as for example for drying wet loose material, for regeneration of loaded absorption material or for chemical reactions, such as for example gasification or combustion of fine grained coal, there are employed preferably vortex or whirl chutes because of their advantageous material and heat exchange. In these chutes a whirling gas streams in vertical direction whereas the treated loose material advances or better to say flows under a constant vertical vortex movement along the whirl chute from its inlet to its outlet. It is desirable that the whirl (i.e. fluidizing) gas impart over the entire flow leading floor as uniform whirling condition as possible. A uniform whirling condition is obtained when the velocity of the whirling gas in any point of the whirl chute constantly amounts to a definite multiple preferably 1.2 to 2 times the actual whirling velocity of respective solid particles.
If due to the treatment the bulk density of the solid particles is changed during their travel through the whirl chute, so is changed also the velocity of the center of vortex of the particles along the whirl chute. As a consequence, at a constant velocity of the whirl gas along the whirl chute no uniform whirling condition of the solid particles can be attained. A typical example of a gradual reduction of the bulk density of the solid particles is regeneration of wet absorption materials such as aluminum oxide or activated carbon. In this case the change of the bulk density between the inlet and outlet of the whirl chute is mostly more than 50 percent. As a result uncontrollable and undesirable intermixtures, deformations and time delays of solid particles treated in the whirl chutes take place in such cases.
Even an incorporation of dams, narrow passages and the like in the whirl chutes does not result in the desired uniformity of the treatment of the solid particles.